Camelot on Thursday announced it had received a "valid claim" on the £33 million Lotto jackpot winning ticket bought in Worcester.
The winner, Camelot said, wants to remain anonymous.
Married couple David and Carol Martin, both 54, from Hawick in the Scottish Borders, had only be announced as winners of the other half of the £66 million jackpot - the UK's biggest Lotto prize.
Thursday's announcement followed days of speculation around a claim made by Worcester grandmother Susanne Hinte who contacted Camelot last Friday to say she had the winning ticket, but had put through the wash.
The Telegraph on Thursday reported that it understood Camelot had already excluded Hinte, 48, from their hunt for the mystery winner.
The paper reported that Camelot had not bothered to check CCTV footage from the newsagents where Hinte claimed she bought the ticket.
A senior security source the newspaper: “If Miss Hinte was even suspected of winning the lottery the first thing Camelot would have done is grab that CCTV footage. The footage is proof of where she bought the ticket and at what time.”
Hinte bought her ticket from Ambleside News in Worcester. Hamsa Patel, who runs the newsagents, has said that he has CCTV footage of the sale which he could make available to Camelot.
Camelot are understood to have declined the offer.
Camelot earlier said it had not released details of the shop where the winning ticket was bought and no retailer had been informed that they sold the winning ticket. It is understood Ambleside News was simply told that the winning ticket had been sold in Worcester.
Camelot on Wednesday warned it wold take action if it believed someone had "intentionally attempted to defraud the National Lottery".
According to CPS sentencing guidelines, fraud by false representation can be punished by a maximum term of ten years jail.
A Camelot spokeswoman said: "With prizes of this size, it's perfectly normal to receive lots of claims from people who genuinely think that they may have mislaid or thrown away what they believe was the winning ticket.
"That's what we're seeing now - and we are looking into all of these claims as part of our efforts to find the rightful ticket-holder.
"However, if we believe that somebody has intentionally attempted to defraud the National Lottery, then, just like any other company, we reserve the right to take whatever action we consider is appropriate."
Camelot would not however, comment on what, if any action they had taken against attempts to defraud it.
In August 2012 shop keeper Farrakh Nizzar was jailed for 30 months after trying to claim a winning £1 million lottery ticket belonging to a pensioner couple. Camelot became suspicious of Nizzar when he couldn't answer basic questions about the ticket so checked CCTV footage where his scam was uncovered.
Under the terms of its licence, Camelot has discretion to pay prizes in respect of stolen, lost or destroyed tickets if a player has submitted a claim in writing within 30 days of the draw.
Camelot has said that even if a winner with a stolen, lost or damaged ticket is identified, the money will not be paid out for at least 180 days so others can get in touch. If the Worcester prize goes unclaimed after a deadline of July 7, the money will be donated to good causes, the lottery operator added.
On Wednesday a friend of Hinte's told The Sun that she hadn't "believed" her story from "day one".
The woman, whom the newspaper did not name, said: "I don't think the ticket is genuine. When I saw it I knew that it wasn't right."
She added: "I think she bought a later ticket after the day she says she had."
The Sun also revealed that Hinte had previously tried to falsely claim a £200 prize on a scratch card she said had been damaged after she dropped it in a puddle - only two of the three required £200 symbols were visible.Suggest a correction